16:8 Fasting Timer
ArcFast tracks the 16-hour fast and 8-hour eating window at the heart of 16:8. Start your fast, watch the timer and your fasting phase, and end it when your window opens — with no ads and no account required.
What is 16:8 fasting?
16:8 is a form of intermittent fasting that splits your day into a 16-hour fast and an 8-hour eating window. You eat all of your meals inside the 8-hour window, then fast for the remaining 16 hours, including while you sleep.
A common schedule looks like this:
- Eat: 12 PM – 8 PM
- Fast: 8 PM – 12 PM the next day
The exact hours are flexible — the point is the ratio, not a fixed clock. A timer keeps the boundary clear so you are not guessing when your window opens.
How to use ArcFast for 16:8
- Choose or create a 16:8 plan — pick the preset or set your own hours.
- Start your fast when you finish your last meal.
- Watch the timer and phase to see time remaining and where you are in the fast.
- End your fast when your eating window opens.
- Log or scan a meal if you want a record of what you ate — try the AI calorie scanner.
New to fasting phases? The fasting phases explained page walks through what the labels mean.
Who 16:8 may fit
16:8 tends to appeal to people who want a simple, repeatable routine. It may suit you if you are:
- New to intermittent fasting and want an approachable starting point.
- Looking for a daily rhythm rather than occasional long fasts.
- Comfortable eating within a set window most days.
That said, 16:8 is not right for everyone, and it is not a guaranteed path to any specific result. Choose it because the routine fits your life, not because it promises an outcome.
Common 16:8 mistakes to avoid
- Not drinking enough water. Hydration matters during the fasting window.
- Skimping on protein and nutrients. A shorter eating window still needs balanced meals.
- Treating the eating window as unlimited. 8 hours to eat is not a license to overeat.
- Ignoring medical context. If a health condition or medication is in the picture, talk to a professional first.
Fasting affects everyone differently, and your body may vary from day to day. ArcFast is a tracking tool, not medical advice.
Frequently asked questions
Can I change my eating window?
Yes. You can shift your 16:8 window to fit your schedule — for example eating noon to 8 PM, or 10 AM to 6 PM — or build a fully custom window in ArcFast.
Can I do 16:8 every day?
Many people run 16:8 daily, but it is not right for everyone. Listen to your body, keep meals balanced, and check with a healthcare professional if you are unsure whether daily fasting suits you.
Does coffee break a fast?
Plain black coffee, tea, and water are generally considered fine during a fast by many people, while anything with calories — milk, sugar, sweeteners — can affect it. Definitions of breaking a fast vary, so use your own goal as the guide. ArcFast times the window; what counts as breaking your fast is up to you.
Is 16:8 safe?
16:8 works for many people, but it is not right for everyone, and no app can promise it is risk-free. It may not suit you if you are pregnant, diabetic, under 18, managing an eating disorder, or under medical supervision. Talk to a healthcare professional before starting.
Get ArcFast for iPhone
Start with the free fasting timer. Premium plans available.